Conventional high performance liquid chromatography (HPLC) involves the passage of a sample through a bed of beads. It is not possible, however, to achieve a perfectly packed bed. Heterogeneities in packed beds give rise to zone broadening, which is detrimental to resolution and solute detection and identification. Further disadvantages of packed beds are the time-consuming and expensive steps involved in preparing the beads, sieving the beads to isolate those of the desired size, and packing the column with the beads.